Interview: Jack, BlockBeats, Vision, Metastone

Editor: Sharon, BlockBeats

Currently, the blockchain industry is facing a triple dilemma: scalability, security, and lack of decentralization - the lack of trustless cross-chain communication, the lack of Rollup scalability when transaction volume grows large enough, and the inability to maintain high levels of security and decentralization when aiming to improve throughput. This is a long-standing problem, and the essence of the problem lies in finding a way to securely store data in a smaller, lighter container without using too much or too expensive storage devices.

Most of today's blockchains are single-layered, with the core functions of blockchain, including execution and consensus, occurring and executed by the same group of validators. The monolithic architecture is difficult to scale because each transaction must be executed by a full node, resulting in bottlenecks. Modular blockchains, on the other hand, outsource at least one of the four components (consensus, data availability, execution, and settlement) completely to an external chain.

And Celestia is the first modular blockchain network and a cloud computing network for Web 3. It is a pluggable consensus and data availability layer that allows anyone to quickly deploy decentralized blockchains without the cost of bootstrapping a new consensus network. Some in the industry believe that Celestia is the most important underlying innovation in the blockchain industry since Ethereum. Both Ethereum and Celestia are building secure foundational layers. BlockBeats exclusively interviewed Celestia's co-founder and COO Nick White at the TOKEN 2049 conference to explore the relationship between Celestia and Ethereum, as well as the story behind Celestia.

Without Celestia, Ethereum cannot scale Rollups

In these three dilemmas, the lack of scalability has the greatest impact - only by enhancing the scalability of the blockchain can hundreds of millions of people also open the window to the chain. This is also the biggest dilemma faced by mainstream blockchains including Ethereum. Currently, Ethereum has extension solutions such as Optimism, ZKsync, and Starknet. However, the data availability of these extension solutions is heavily dependent on Ethereum itself. At the same time, Ethereum's gas fees are still very expensive.

Previously, Ethereum founder Vitalik described his vision of the ultimate form of the Ethereum blockchain, which extensively depicted a new Ethereum built by Rollup and DA. This undoubtedly points to the way forward for Ethereum in the next decade - modularity.

Related reading: "Modularization: The Breakthrough Path for Ethereum in the Next Decade".

BlockBeats: Can you introduce yourself and your background?

Nick: Of course. My name is Nick White. I am the Chief Operating Officer (COO) of Celestia Labs. We are building Celestia, which is the first modular blockchain network. This means that Celestia supports a new paradigm for building blockchains, where we no longer try to accomplish all functions within one protocol. Instead, we divide the protocol into different layers, each focusing on specific functions. These layers can then be recombined to build blockchains and applications.

Therefore, Celestia focuses on the consensus and data availability layers of the stack, without performing any execution. Execution is achieved through Rollup (one of the Layer2 solutions). People can deploy Rollup on top of Celestia, and Celestia provides a scalable decentralized block space for people to build on. So you can think of us as a first layer specifically designed for the future centered around Rollup, to extend Rollup.

BlockBeats: When did you first start using modular blockchain technology?

Nick: It all started with two whitepapers that were published in 2018 and 2019. The first whitepaper, titled "Data Availability Sampling and Fraud Proofs," was co-authored by Mustafa Albasan, co-founder of Celestia, and Vitalik. In this paper, they demonstrated how to build a blockchain that can scale with the number of nodes in the network, thus solving the scalability problem.

Then, based on his previous work, he wrote another white paper called "Lazy Ledger". "Lazy Ledger" is a continuation and extension of the concept of data availability expansion, in which he proposed a new idea - to build a blockchain that is only responsible for data availability and does not execute any transactions. At that time, he called it "client-side smart contract".

Related reading: "Understanding Celestia and Fuel: Modular blockchains to watch in 2023."

The client of blockchain will execute transactions independently of the first layer, which is currently Rollup. Rollup is actually the off-chain execution of smart contracts and applications. Therefore, the concept of modular blockchain is indeed introduced in "Lazy Ledger". Later, when Rollup appeared, it further demonstrated how the entire system works, because Rollup can make the execution layer as scalable as data availability sampling.

BlockBeats: Will the launch of Ethereum's project sharding reduce the cost of Layer2, and will it have an impact on Celestia?

Nick: ETH sharding, which is Ethereum, has actually shifted its roadmap to mimic the way Celestia is being built. Prior to this, they were building ETH 2.0, which is the sharding technology, but at the end of 2020, they decided to pivot and follow Celestia's building approach. Over time, they gradually aligned their architecture more closely with Celestia's model. So, Danksharding is essentially a different implementation of the similar idea that Celestia is pursuing.

However, there are several differences between them, the first being time. Celestia will be launched in a few months, while Danksharding is still in the design and research phase, making it difficult to know when it will be launched. I don't think they have even set a date yet, but they do have Proto-Danksharding, which is EIP-4844, but this will only result in a small one-time increase in Ethereum's block space.

Based on the deployment needs we have seen for Layer2, I believe that this is far from sufficient to provide the required throughput. Therefore, Celestia will be launched when people want to deploy Rollup in large numbers. I believe that without Celestia, Ethereum will not be able to scale Rollup. In the long run, when Danksharding is launched, the problem is that it is similar to a data availability layer attached to a single first layer, which is the original Ethereum chain.

Therefore, Ethereum has a lot of technical debt and baggage that needs to be developed on top of it, while Celestia has the opportunity to start from scratch, so there won't be as much state bloat. We don't need to execute, our network is very lightweight and simplified, while Ethereum doesn't have this luxury, they still need to carry the burden of Ethereum Layer1, these are some of the differences I see.

DAS is more trustworthy than DAC

Allowing users to securely own their data and the assets represented by that data helps to dispel various concerns about asset security for ordinary users, and is helpful in guiding the next billion users into Web3. Therefore, an independent data availability layer will be an indispensable part of Web3. Data Availability (DA) essentially means that light nodes do not need to store all data or maintain the state of the entire network in a timely manner without participating in consensus.

The current mainstream ways to verify data are DAS (Data Availability Sampling) and DAC (Data Availability Committee). The former verifies whether a block has been published by downloading some randomly selected blocks, while the latter confirms that it has received data by signing each update of the state with its statutory number of people.

The industry generally believes that when an independent data availability layer is a public chain, it is superior to a usability committee composed of a group of subjective individuals. This is because if enough committee members' private keys are stolen, making off-chain data availability unavailable, users' funds and data security will be greatly threatened. Nick pointed out that what Celestia is currently doing is to make the data availability layer more decentralized - equivalent to providing an independent DA public chain with a series of validation nodes, block producers, and consensus mechanisms to improve security levels.

BlockBeats: In the DA market, all DA layer mainly accepts data from Layer 2 and Layer 3. However, we know that most of Layer 3 cannot send their data to the DA layer due to data staking. But Polygon will use bridging to receive this data. I would like to know your thoughts on this and what method Celestia will use to receive data from Layer 3?

Nick: Its purpose is to ensure that the bridge verifies the availability of data on Celestia. Therefore, third parties can publish their data on Celestia, but update their status on another chain, such as Ethereum Layer1, Optimism, Polygon, etc. Aggregated contracts on those chains can verify the availability of data on Celestia through this bridging method. Therefore, we can help extend this point.

BlockBeats: In the current DA market, EigenLabs has also launched an EigenDA. At the same time, EigenLabs has borrowed the original distributed nodes of Ethereum to protect the security of other networks and reduce node operations. So, what is your opinion on this?

Nick: Refinancing is an interesting idea that allows you to use existing funds, such as collateral, to collateralize a new protocol. However, it does not fundamentally expand the blockchain. It is just a way to launch a new protocol without issuing new tokens. As for EigenDA, the problem is that their design is not actually about data availability. Data availability here refers to the concept you think of when you think of Ethereum, Danksharding, or Celestia. Because EigenDA is only a data availability committee, which is a multisignature account, someone tells you that the data is available, but you cannot verify it yourself. Therefore, EigenDA cannot be compared with Celestia, and they are not completely identical products.

Another issue is that if they use re-mortgaged ETH or any non-EigenDA token to secure EigenDA, they cannot punish data withholding attacks. Data withholding attacks are unattributable faults, which means that you cannot prove that data has been withheld from smart contracts on Ethereum Layer1 or any other entity. Therefore, if someone actually withholds data, they will not be able to punish re-mortgaged ETH. This way, you can actually attack EigenDA at zero cost. So, I think this is a deep design issue with EigenDA. This is my view on EigenDA.

BlockBeats: During the process of verifying data, some off-chain data availability layers choose to use DAC to protect their data, while other data layers choose to use DAS. What are your thoughts on DAC and DAS?

Nick: Blockchain is actually a verifiable computer. Therefore, you don't need to trust anyone else, such as a committee. Because the purpose of decentralization is achieved by allowing end users to verify the chain. Therefore, the data availability committee is not actually a blockchain, because when using DAC, by definition, you must trust a committee. In contrast, data availability sampling is a method of directly verifying the chain by sampling. Therefore, from the perspective of verifiability, it is a true blockchain. You don't need to trust Celestia's validators, you can verify it yourself. Even if they try to deceive or collude, they cannot fool you. This is a fundamental difference, very important, and people should be aware of this. This is also what I said before, EigenDA is not the same as Celestia because it is a DAC, and you cannot really compare them.

BlockBeats: Are there any additional benefits for DAS when adding or removing nodes in the network?

Nick: Of course. One of the superpowers of networks like Celestia is that they use data availability sampling, which means that you can increase the size of blocks as the number of nodes in the network grows. This is incredibly powerful because in a single-chain system, no matter how many people are running nodes, you can only use the same block size. But in Celestia, as more nodes join and sampling begins, you can actually increase the size of blocks.

We hope to create a culture where users can run nodes on their wallets or browsers. This means that as more users join the network, the number of nodes increases, allowing for larger blocks and more block space for new users and applications. Therefore, there is a positive feedback loop where users are actually providing expanded scale for their own applications.

Future may use KZG commitment

The Quantum Gravity Bridge (QGB for short) is a data availability bridge between Celestia and Ethereum. It is deployed on Ethereum by Celestia, and then the operators of Ethereum Layer2 can publish their transmission data to the Celestia network, which is then put into blocks by Celestia's Proof of Stake (PoS) validators. Then, this data is forwarded from Celestia to Ethereum in the form of data availability proof. The proof is signed by Celestia validators and contains the Merkle root of L2 data, proving that the data is available on Celestia.

QGB contract verification relies on the signature on the DA proof from Celestia. Therefore, when the Layer2 contract on Ethereum updates its state, it does not rely on the transmitted data published to Ethereum, but checks whether the correct data is provided on Celestia by querying the DA bridge contract. The contract will give a positive response to any valid proof forwarded to it previously, otherwise it will return a negative response. Nick pointed out that Celestia will provide high throughput data availability for Ethereum Layer2, which is more secure and cheaper than other off-chain data availability solutions.

BlockBeats: Do you think that the cost of quantum gravity bridge is more expensive or cheaper than EigenDA?

Nick: EigenDA's problem is that they haven't released any information about how they actually build it. So, without the code, it's hard to know what it will look like. I think, for EigenDA, based on their construction, it may incur expensive proof costs because you have to generate KZG commitments (Kate-Zaverucha-Goldberg, polynomial commitment scheme) and verify signatures on Ethereum, such as verifying a bunch of signatures for each batch. So this could actually consume a lot of Gas. The advantage of QGB is that we designed it specifically to minimize Gas costs.

First of all, we have batch processing. Just like having multiple Celestia blocks, they are all batched into one block, then a commitment is generated, signed, and published to Ethereum. So, there is no need to pass and verify each block, you only need to perform one operation in a batch, which significantly reduces the gas cost of verifying the commitment.

Secondly, we are also building a zero-knowledge QGB, which will verify all these signatures through zero-knowledge proofs, further reducing the gas cost of verifying commitments on Ethereum Layer1. Verifying commitments on Ethereum Layer1 is a significant expense for any off-chain DA due to gas costs. Additionally, it is currently difficult to know the actual DA cost of paying for data on Celestia and EigenDA. I believe the cost will be very, very low in either case, to the point where I doubt it will be a differentiating factor unless Celestia suddenly becomes congested or other circumstances lead to very high costs.

BlockBeats: You just mentioned KZG, but why hasn't Celestia used KZG yet? What is the reasoning behind this decision?

Nick: Yes, the issue with KZG commitments is that they are still quite new and the computation speed is very slow. Therefore, creating blocks using KZG commitments would be more expensive. Additionally, as the block size increases, you would have to compute more and more opening values, which would slow down the process. Therefore, Celestia made a very practical decision to use a regular Merkle tree (hash tree) with fraud proofs instead.

But the problem is, if it becomes practically feasible, we can easily replace it with KZG commitments. Excitingly, a few weeks ago at the SBC (Blockchain Science Conference), Dankrad Feist, a researcher at the Ethereum Foundation, shared some promising research on KZG hardware acceleration, and we are keeping an eye on this situation. If there are any changes and improvements, we will definitely consider replacing it. However, KZG will add a lot of complexity, so this is a challenge.

BlockBeats: I want to ask some questions about Rollkit, a modular rollup framework. What role do you think Rollkit will play in the future?

Nick: First of all, people should know that Celestia is completely neutral. In fact, we are currently working with almost every rollup SDK to integrate Celestia as a DA option. We started Rollkit before open-source rollup frameworks existed because at the time there were Layer2 solutions, but they were all trying to build their own singular thing instead of trying to build a software SDK for anyone to build their own rollup. That's why we incubated Rollkit.

One of the unique features of Rollkit, in my opinion, is that it is the first concept designed without being tied to Ethereum or involving smart contract settlements. Therefore, it is more suitable for running Sovereign rollups. Another important aspect is that Sovereign Rollkit is compatible with ABCI (Application Blockchain Interface), so any Cosmos SDK application or execution environment compatible with ABCI can be compatible with it. People have already used many different virtual machines and made them compatible with ABCI, and then launched them on Rollkit. This is very important because it opens up another ecosystem for building rollups. Another great thing is that the Rollkit team has built a fraud proof system for Cosmos SDK applications. Therefore, it is actually possible to build an optimistic rollup on Rollkit, which is very exciting.

BlockBeats: Do you have anything to say to Chinese developers or practitioners?

Nick: We are very excited to have more presence in China, and we know that China has played such an important role in the origin of blockchain and cryptocurrency from a very early stage. China has so many talented engineers and users, and the Chinese community is full of passion. So, we are very much looking forward to engaging and participating with it. I have lived in Hong Kong for a year and a half and have traveled to many parts of China. I love Chinese culture, and I really appreciate the mentality of the Chinese people. They are full of eagerness, have a builder's mentality, and a fighter's mentality, which I really like.

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